Mufflers with spark arresters attenuate exhaust gas noise and sparks from internal combustion engines. However, mufflers add size, weight, and power-robbing backpressure to an engine. Small vehicles, such as all terrain vehicles (ATVs), motorcycles, and snowmobiles, need high power-to-weight ratios for optimum performance. Small size and low weight help the driver maneuver the vehicle through off-road obstacles. A high power-to-weight ratio helps the vehicle climb and accelerate, and increases available load-carrying capacity. While an effective muffler adds weight and reduces horsepower, quiet operation without exhaust spark emissions not only enables the vehicle to meet mandatory government regulations, but increases the vehicle acceptance by both the user and others wishing to enjoy the outdoor environment.
Typical commercially available mufflers reduce noise levels to regulation standards. However, the noise level may still not be acceptable to users and others in the vicinity. Manufacturers may be reluctant use mufflers that decrease the noise level much below government mandates since such reductions usually result in an increase in muffler weight, size, and/or backpressure. Muffler noise reductions may be increased with additional baffles and chambers or by increasing size—the very changes that also increase weight and backpressure. Such changes also increase the complexity and cost of manufacture.
Backpressure occurs when exhaust gases do not have a direct, easy-flow exit route. The engine must push the gases out through a tortuous (although noise-canceling) path of chambers, baffles, tubes, and turns. Thus backpressure restricts power that would have been available to propel the vehicle.
Therefore, a need exists for a muffler that decreases backpressure without increasing noise, or conversely, that decreases noise without increasing backpressure. Further advantages would result with simplified manufacturing and lighter weights.